Calm, clear day dangerous time to spray

A temperature inversion keeps cold air down and fine droplets of chemical hang in the air until a breeze blows them to an unintended crop

The storm has passed and conditions are calm. Farmers are eager to get out to the fields and spray the crops after a weather-induced delay.

But don’t do it, says Andrew Thostenson, a pesticide program specialist with North Dakota State University.

He said that is one of the worst times to spray because conditions favour an inversion, which is the presence of cold air near the surface that causes spray drift and chemical spread where it isn’t wanted.